Effect of withdrawing an immunomodulatory feed additive from lactating cow diets on peripheral blood mononuclear cell proliferation.

Supplementation of immunomodulatory feed additives, such as OmniGen AF (OG), helps to maintain immune competency; however, it is unknown if immune benefits persist in lactating cows after OG is removed from the diet. The aim of this trial was to evaluate the effect of withdrawing OG from the diet on peripheral blood mononuclear cells (PBMC) proliferation of midlactation dairy cows. Multiparous Holstein cows (N = 32), blocked by parity (2.7 ± 0.8) and days in milk (153 ± 39 d) were randomly assigned to one of the two dietary treatments within each block: diets were top dressed with either OG (56 g/d/cow) or placebo (CTL, 56 g/d/cow). Cows were housed in the same free-stall pen and individually fed once per day through Calan gates. All cows were fed the same diet containing OG for at least 1 yr before the onset of treatments. Cows were milked three time per day and milk yield was recorded at each milking. Milk samples were collected from three consecutive milkings weekly and composition analyzed. Body weight (BW) and condition score were measured weekly. Blood samples were collected at -1, 1, 3, 5, and 7 wk relative to the onset of treatments for the isolation of PBMC. The PBMC were cultured with concanavalin A (ConA) and lipopolysaccharides (LPS) for 72 h in vitro to determine proliferative responses. Prior to the experiment, cows in both treatments had similar disease incidence. During the experiment, cows did not show symptoms of disease. Withdrawing OG from the diet did not affect (P ≥ 0.20) milk yield or composition, intake, or BW. Compared with CTL, feeding OG maintained greater body condition score (2.83 vs. 2.92, P = 0.04). Regardless of time, relative to CTL, PBMC isolated from cows fed with OG had a greater proliferative rate when stimulated with LPS (stimulation index: 1.27 vs. 1.80, P = 0.05) and tended to have greater proliferation when stimulated with ConA (stimulation index: 5.24 vs. 7.80, P = 0.08). In conclusion, withdrawing OG from the diet of midlactation cows reduced proliferative response of PBMC suggesting that the immunomodulatory role of OG is lost as early as 1 wk after its withdrawal from the diet of lactating dairy cows.

We hypothesized that withdrawing an immune modulatory feed additive (OmniGen AF [OG]) from the diet would reduce immune function of lactating dairy cows. Thus, this short communication aimed to examine if withdrawing OG from the diet of the lactating dairy cow could affect her immune function. Thirty-two midlactation Holstein cows were fed OG prior to the experiment. In the 8 wk experiment, OG was removed from the diet of 16 cows, but remained in the diet of the other 16 cows. We observed that withdrawing OG did not affect the intake and milk production but reduced the ability of the circulating immune cells of the cow to proliferate when challenged with mitogens in vitro. These results suggest withdrawing OG from the diet reduces the immune function of lactating dairy cows, increasing the risk of developing diseases.

Effect of an Immunomodulatory Feed Additive in Mitigating the Stress Responses in Lactating Dairy Cows to a High Concentrate Diet Challenge.

Dairy cows are often exposed to multiple stressors in a lactation-cycle, with sub-acute ruminal acidosis (SARA) a frequent example of nutritional stress. SARA affects ruminal and intestinal equilibrium resulting in dysbiosis with localized and systemic inflammation impacting animal health and productivity. OmniGen-AF (OMN, Phibro Animal Health Corporation, Teaneck, NJ, USA) is a feed product recognized for modulating innate immune function, especially during periods of stress. The objective of this study was to determine the effects of OMN in lactating dairy cows fed a high-starch, low-fiber diet. Twenty-four blocked cows were assigned to control or treatment (55 g/d). After the additive adaptation (49 d) cows were fed the challenge diet (28 d). Milk, rumination and pH were continuously recorded; components, rumen fluid, and blood were taken in multiple time-point and analyzed. Results showed that the challenge decreased the rumination, shifted ruminal fluid composition, decreased milk production and the components, and slightly increased the time below pH 5.5, with no differences between groups. The treatment produced greater rumen butyrate and lower lactate, prompter regeneration of red blood cells, increase of neutrophils, lower paraoxonase, gamma-glutamyl-transferase, and ß-hydroxybutyrate, with no differences on other tested inflammatory markers. Results show that OMN helps modulating some of the metabolic and immunological responses to SARA.

Effect of vitamin D source and dietary cation-anion difference in peripartum dairy cows on calcium homeostasis and milk production.

The objective of this experiment was to determine the effects of dietary vitamin D source on serum calcium (Ca), urinary Ca excretion, and milk production when fed in combination with a prepartum acidogenic negative dietary cation-anion difference (DCAD) diet. Nonlactating, pregnant multiparous cows (n = 15), balanced for breed (Holstein n = 9 and Jersey n = 6), and previous mature equivalent milk production, were assigned to one of three treatments (five cows/treatment), consisting of a control (PCH; positive DCAD, 8.9 mEq/100 g DM) and two negative DCAD diets (-15.4 mEq/100 g DM), one with vitamin D3 (cholecalciferol; NCH) and one with 25-hydroxyvitamin D3 (calcidiol; NCA; DSM nutritional products). The treatments were formulated to provide 1.95 mg/d of vitamin D and were fed 28 d prior to expected calving date. Delivery of vitamin D sources was accomplished by manufacture of a pellet and 2 kg of these pellets were individually fed simultaneously each day along with 2 kg of ground corn daily at 0800 hours. Negative DCAD treatments were formulated to provide 0.46 kg/d of Animate (Phibro Animal Health) and, if needed, additional Animate was top-dressed at each feeding to achieve a urine pH between 5.5 and 6.0 based on the previous day's urine pH. Close-up cows had ad libitum access to chopped bermudagrass (Cynodon dactylon L.) hay and hay intake was measured using SmartFeed Pro systems (C-Lock Inc.; Rapid City, SD). Prepartum urine and serum samples were collected weekly and serum was collected 36, 48, and 72 h post-calving. Prepartum dry matter intake (DMI) as a percent of body weight was not (P = 0.66) affected by treatments. Cows fed NCH and NCA had greater (P = 0.02) prepartum serum Ca than PCH and tended to have greater urinary Ca excretions (P = 0.10). Average postpartum serum Ca (mg/dL) was greater (P = 0.05) for cows fed NCH (8.8) compared with PCH (7.8), whereas NCA (8.4) was numerically intermediate and not (P > 0.05) different from either of the other treatments. Postpartum DMI was not affected by treatment (P = 0.39). Daily milk yield (MY) (kg/d) was greatest (P < 0.01) for NCA (37.5) compared with the other treatments and NCH (34.1) was intermediate and greater than PCH (29.9). These results suggest that an acidogenic prepartum diet in combination with vitamin D was effective in maintaining peripartum serum Ca and the 25-hydroxy form of vitamin D improved MY compared with NCH in early lactation.

Impact of heat stress and a feed supplement on hormonal and inflammatory responses of dairy cows.

The aim of this trial was to evaluate the effects of an immunomodulatory supplement (OmniGen AF, OG; Phibro Animal Health Corp.) and heat stress on hormonal, inflammatory, and immunological responses of lactating dairy cows. Sixty multiparous Holstein cows were randomly assigned to 4 treatments in a 2 × 2 factorial arrangement using 2 environments: cooled using fans and misters, or noncooled, and 2 top-dressed feed supplements (56 g/d): OG or a placebo (CTL). Temperature-humidity index averaged 78 during the 8-wk trial. Blood was drawn to analyze cortisol, prolactin, and circulating tumor necrosis factor (TNF)-α and IL-10. Peripheral blood mononuclear cells (PBMC) were isolated and stimulated with hydrocortisone, prolactin, or lipopolysaccharide (LPS), individually or in several combinations, to assess induced proliferation and cytokine production. At d 52, 6 cows per treatment were injected i.v. with an LPS bolus (ivLPS) to assess hormone and cytokine responses. For cooled cows, feeding OG increased plasma cortisol concentration relative to CTL. Noncooled cows fed CTL had lower circulating TNF-α concentrations than noncooled-OG and cooled-CTL cows, with cooled-OG intermediate. Hydrocortisone+LPS-stimulated PBMC from OG cows tended to proliferate more than CTL. Relative to cooled cows, PBMC from noncooled cows produced more TNF-α and IL-10 when stimulated with LPS. Following ivLPS, cooled-OG cows had a greater cortisol response than the other treatments. In conclusion, OG supplementation enhanced cortisol release under basal condition and induced inflammation with cooling compared with CTL. This suggests that heat stress inhibits OG-mediated cortisol release. Heat stress seemed to enhance the inflammatory responses of PBMC from lactating cows. However, OG supplementation promoted PBMC proliferation under stress, or in the presence of hydrocortisone.

Influence of an immune-modulatory feed supplement on performance and immune function of beef cows and calves preweaning.

The ability to positively alter immune and stress response with nutritional compounds is of great interest and importance to the beef industry. There is a proprietary product (OmniGen-AF [OG]; Phibro Animal Health, Quincy, IL) reported to have performance-enhancing benefits by altering animal response to stress and immune challenges. The objective of this 2-yr research project was to study the effect of supplementing OG to beef cows and their calves on breeding and growth performance. One hundred and twelve multiparous beef cows and 48 primiparous cows were randomly assigned to treatment in year 1; control (CON, no OG; n = 56 multiparous and 24 primiparous) or treatment (OG fed at 8.8 g/100 kg body weight [BW]; n = 56 multiparous and 24 primiparous). Multiparous cows (mean ± SD = 6.4 ± 0.4 yr; BW = 589 ± 9.2 kg; body condition score [BCS] 6.2 ± 0.07) were used in both years of the experiment and primiparous cows (mean ± SD = 2.1 ± 0.04 yr of age, weighed 400 ± 7.5 kg, and BSC of 5.6 ± 0.06) were only used in the first year of the experiment. CON and OG supplements were offered over two production cycles beginning in December approximately 60 d prior to projected calving through pre-breeding in May of each year. Calves from treatment cows were offered treatments in a creep supplement limited to a daily rate of 1% as-fed of BW prorated for 3-d/wk feeding from mid-July through weaning with OG offered at 8.8 g/100 kg BW. Primiparous cow's BW, BCS, and calf performance were not affected by treatment (P ≥ 0.15) in year 1. BW of multiparous OG cows tended (P = 0.10) to be heavier at weaning in year 1 and was greater (P = 0.05) at the onset of the experiment in year 2. Body condition of OG cows was greater (P ≤ 0.02) at weaning in both years 1 and 2, as well as at the onset of the experiment in year 2. Calves fed OG from the mature cows gained more (P = 0.05) BW during the creep feeding period than CON. Core body temperatures of OG heifers measured during the late summer with intravaginal temperature data loggers tended (P ≤ 0.10) to be less at 1400 and 1700 hours and were less (P = 0.05) at 1800 hours than CON heifers. Feeding OG did not result in changes (P = 0.25) in serum titer response to the BVD virus of calves during year 2. The results of the current experiment indicate feeding OG to beef cows and calves can result in improvement in BCS of cows, enhance weight gain of calves preweaning, and reduce heat loads in heifer calves during the late summer.

Effects of feeding an immunomodulatory supplement to heat-stressed or actively cooled cows during late gestation on postnatal immunity, health, and growth of calves.

Heat stress during late gestation negatively affects the physiology, health, and productivity of dairy cows as well as the calves developing in utero. Providing cows with active cooling devices, such as fans and soakers, and supplementing cows with an immunomodulating feed additive, OmniGen-AF (OG; Phibro Animal Health Corporation), improves immune function and milk yield of cows. It is unknown if maternal supplementation of OG combined with active cooling during late gestation might benefit the developing calf as well. Herein we evaluated markers of innate immune function, including immune cell counts, acute phase proteins, and neutrophil function, of calves born to multiparous dams in a 2 × 2 factorial design. Dams were supplemented with OG or a bentonite control (NO) beginning at 60 d before dry off and exposed to heat stress with cooling (CL) or without active cooling (HT) during the dry period (∼46 d). At birth, calves were separated from their dams and fed 6.6 L of their dams' colostrum in 2 meals. Calf body weight and rectal temperature were recorded, and blood samples were collected at birth (before colostrum feeding) and at 10, 28, and 49 d of age. Calves born to either CL dams or OG dams were heavier at birth than calves born to HT or NO dams, respectively. Concentrations of serum amyloid A were higher in the blood of calves born to OG dams relative to NO and for HT calves relative to CL calves. In addition, calves born to cooled OG dams had greater concentrations of plasma haptoglobin than calves born to cooled control dams. Neutrophil function at 10 d of age was enhanced in calves born to cooled OG dams and lymphocyte counts were higher in calves born to OG dams. Together these results suggest that adding OG to maternal feed in combination with active cooling of cows during late gestation is effective in mitigating the negative effects of in utero heat stress on postnatal calf growth and immune competence.